You should use quotation marks or set the text in italics if there's a risk the reader won't understand what you're asking. You usually don't have to do this when you're naming a noun, but using quotation marks is never wrong.
Consider these examples:
What's matter?
What's matter?
What's cooking?
What's cooking?
The expression "What's cooking?" is American slang for "What are you doing?". If you don't mark "cooking" to distinguish it from the other text, your reader won't know that you're asking about the word rather than their activities. As you can see from this example, words can have hidden meanings, so it's safer to use the quotation marks.